search for host in string PHP

searchstring.php

<?php

//simulating the array from string:
$s = '
[2018-02-19 14:08:32] [info] status=GOOD&unit_status=GOOD&hostname=acme
[2018-02-19 14:08:32] [alert] Wrong status! (Not "DEGRADED")
[2018-02-19 14:08:37] [info] Request with params {"status":"GOOD","unit_status":"GOOD","hostname":"joe"}
[2018-02-19 14:08:37] [info] status=GOOD&unit_status=GOOD&hostname=joe
[2018-02-19 14:08:37] [alert] Wrong status! (Not "DEGRADED")
';

$ar = explode("\n",$s);
$hostsToFind = [
    'acme'=>0,
    'joe'=>0,
    'bleh'=>0,
];

foreach($ar as $inputRow){
    if (preg_match('/&hostname=(.+)$/', $inputRow, $token)) {
        $host = $token[1];
        if (array_key_exists($host, $hostsToFind)) {
            $hostsToFind[$host]++;
        }
    }
}
foreach($hostsToFind as $host => $found) {
    if (!$found) {
        echo "Host not found : ".$host."\n";
    }
}